ABSTRACT A Rapid, Near Patient System for Low Blood Volume Testing of Ammonia, Glutamine and Glutamate to Support Recurrent Monitoring of Acute Neonatal Hyperammonemia (SBIR Phase I) In newborns, hyperammonemia (plasma ammonia >150 ?mol/L) is often the first symptom of an underlying urea cycle disorder (UCD), fatty acid oxidation defect or severe liver disease, and affects an estimated 1 in 8,000 births. Clinical symptoms may present as early as the first few days of life and, without prompt medical attention, can rapidly lead to serious brain injury or death. Acute treatment for hyperammonemia includes simultaneous diagnostic evaluation to distinguish the physiologic basis for ammonia accumulation and therapeutic interventions to reduce plasma ammonia levels and prevent permanent neurologic damage. Given the potential severity of symptoms and the rapid rate of disease progression, expedited testing is vital to the survival of affected newborns. Unfortunately, diagnostic testing for hyperammonemia is currently challenging in newborns due to the relatively large blood volume (>3mL) needed for multiple analytes, the requirement for recurrent testing during therapy and technical limitations for ammonia assays. There is a compelling need for better methods to rapidly diagnose and monitor hyperammonemia in newborns using low blood volumes. We propose to develop a novel digital microfluidic system (FINDER) for the rapid, near patient measurement of ammonia, glutamine and glutamate in newborns from very low volumes of whole blood (<50 ?l for all assays). Glutamine and glutamate are critical for ammonia homeostasis and serve as useful biomarkers in certain UCDs. Through this Phase I SBIR project, we will develop sensitive, automated assays capable of measuring all three analytes within 20 minutes. The FINDER Hyperammonemia test panel will allow clinicians to perform repeated testing during acute treatment of blood-volume limited neonates without increasing the risk for iatrogenic anemia. The Phase I Specific Aims include: (1) develop novel enzymatic assays for ammonia, glutamine and glutamate measurement using the FINDER digital microfluidic cartridge; (2) optimize assay conditions and determine preliminary analytical sensitivity and specificity; and (3) feasibility demonstration using patient plasma samples. The key milestone for progression to Phase II will be the successful demonstration of all assays on-cartridge with acceptable sensitivity and precision. In future Phase II efforts, we will expand the panel to include additional analytes (ketones, glucose and/or liver function tests), establish reagent drying protocols for the multiplexed assay and perform full analytical and clinical validations. We will seek FDA approval of the final product, which will initially be marketed for use in newborn patients in U.S. hospitals, with a potential future market towards older patients with known metabolic disorders, who may benefit from the rapid, low blood volume features of the platform.